CVE-2025-53599 is a cross-site scripting (XSS) vulnerability identified in the NAVER Whale browser for iOS versions prior to 3.9.1.4206. This vulnerability arises from improper neutralization of input during web page generation, classified under CWE-79. Specifically, the flaw allows an attacker to execute arbitrary malicious scripts within the context of the browser by leveraging a crafted JavaScript scheme. This means that an attacker can craft a specially designed URL or web content that, when processed by the vulnerable Whale browser, executes unauthorized JavaScript code. Such execution can lead to theft of sensitive information such as cookies, session tokens, or other credentials, manipulation of the Document Object Model (DOM), or redirection to malicious sites. The vulnerability is notable because it affects the iOS version of the Whale browser, which is a Chromium-based browser developed by NAVER, a South Korean internet company. Although no known exploits are currently reported in the wild, the lack of a patch or update at the time of publication indicates that users remain exposed. The absence of a CVSS score suggests that the vulnerability has not yet been fully assessed for severity, but the nature of XSS vulnerabilities typically poses significant risks, especially in browsers where user interaction with web content is frequent and sensitive data is handled. The vulnerability does not require user authentication but does require user interaction, such as clicking a malicious link or visiting a crafted webpage. This vulnerability highlights the importance of proper input validation and output encoding in web browsers to prevent script injection attacks.

For European organizations, the impact of this vulnerability can be significant, particularly for those whose employees or customers use the NAVER Whale browser on iOS devices. The exploitation of this XSS vulnerability could lead to unauthorized access to sensitive corporate data, session hijacking, or the spread of malware through malicious scripts. Organizations in sectors such as finance, healthcare, and government, which often handle sensitive personal and financial information, could face data breaches or compliance violations under regulations like GDPR. Additionally, the compromise of browser sessions could facilitate further attacks within corporate networks, including lateral movement or phishing campaigns. Since the Whale browser is less common in Europe compared to other browsers like Chrome or Firefox, the direct impact might be limited to niche user groups or organizations with ties to South Korea or East Asia. However, any use of this browser in a corporate environment increases the attack surface. The vulnerability could also undermine user trust in secure browsing and lead to reputational damage if exploited in targeted attacks against European entities.

To mitigate this vulnerability, European organizations should take several specific actions beyond generic advice: 1) Identify and inventory all iOS devices within the organization that have the NAVER Whale browser installed, prioritizing those with versions prior to 3.9.1.4206. 2) Enforce an immediate update policy to upgrade the Whale browser to version 3.9.1.4206 or later once available, as this version is expected to contain the fix. 3) Until a patch is applied, restrict or discourage the use of the Whale browser on corporate iOS devices, especially for accessing sensitive or internal resources. 4) Implement network-level protections such as web filtering to block access to known malicious URLs or domains that could exploit this vulnerability. 5) Educate users about the risks of clicking on suspicious links or visiting untrusted websites, emphasizing the specific threat posed by this vulnerability. 6) Monitor browser logs and network traffic for unusual activity that could indicate exploitation attempts. 7) Coordinate with NAVER for timely updates and security advisories to stay informed about patches and exploit developments. These targeted steps will help reduce the risk of exploitation while maintaining operational continuity.